Limited enzymatic cleavage of pig immunoglobulin G and of specific antibodies. I. Different resistance of various antibody types to cleavage by pepsin.
Limited proteolysis by pepsin at pH 4.5 of non-specific pig IgG and of two types of pig anti-dinitrophenyl antibodies revealed striking differences in susceptibility to proteolytic cleavage. The digests were resolved on a column of Sephacryl S-200 and the elution profiles analysed using a computer programme. The individual fragments were characterized by immunoelectrophoresis, SDS-polyacrylamide gel electrophoresis and molecular mass determination. Whereas the non-precipitating antibodies and the non-specific IgG yielded F(ab')2 and pFc' fragments in reasonable quantities, the precipitating antibody proved to be stable even at the 70th h of digestion. The precipitating antibody became susceptible to peptic cleavage only when the pH was lowered to 4.0. It was concluded that the precipitating antibody represents a subclass of pig IgG with an anomalous resistance to proteolysis at acidic pH and that this subclass constitutes only a few per cent, at most, IgG of the healthy, non-immunized animals.
D000818:Animals; D000906:Antibodies / Q000032:analysis*; D002850:Chromatography, Gel; D004140:Dinitrophenols / Q000276:immunology; D006863:Hydrogen-Ion Concentration; D007122:Immunoelectrophoresis; D007074:Immunoglobulin G / Q000032:analysis*; D010434:Pepsin A / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D013552:Swine
D000906:Antibodies; D004140:Dinitrophenols; D007074:Immunoglobulin G; D010434:Pepsin A